According to communication systems in which elements for deinterleaving data, e.g., the number of channels and the depth in the case of convolutional deinterleave, and the number of rows and the number of columns in the case of block deinterleave, are regularly inserted into the data, the deinterleave mode has been conventionally judged by a method in which a protection mode is adopted at the start of receiving or change of modes, or judged by a majority decision method.
FIG. 7 is a diagram illustrating a structure of an error correction apparatus according to a prior art.
An input terminal 102 receives a frame sync signal (fsync). An input terminal 103 receives a Reed-Solomon packet sync signal (psync1). An input terminal 104 receives data (data1).
A deinterleave unit 108 subjects the inputted data (data1) to deinterleaving corresponding to a deinterleave mode (dimode) decided by a deinterleave mode majority judgement unit 109. The deinterleave mode majority judgement unit 109 decides the deinterleave mode (dimode) on the basis of majority decision. A Reed-Solomon decoding unit 110 subjects deinterleaved data (data2) to Reed-Solomon decoding.
An output terminal 111 outputs a Reed-Solomon packet sync signal (psync3) which is synchronized with data (data3). An output terminal 112 outputs a Reed-Solomon packet error signal (perror) which is synchronized with the data (data3). An output terminal 113 outputs Reed-Solomon decoded data (data3).
The operation of the error correction apparatus that is configured as described above will be described.
The data (data1), the frame sync signal (fsync) that is synchronized with the data, and the Reed-Solomon packet sync signal (psync1) that is synchronized with the data are inputted through the respective input terminals 102 to 104 to the deinterleave mode majority judgement unit 109 and the deinterleave unit 108.
The deinterleave mode majority judgement unit 109 extracts a predetermined number of deinterleave modes which are inserted regularly, for example, for each frame, into the data (data1) inputted through the input terminal 104, then makes majority decision, to decide a deinterleave mode (dimode), and outputs the decided mode to the deinterleave unit 108.
Next, the deinterleave unit 108 subjects the data (data1) inputted through the input terminal 104 to deinterleaving corresponding to the decided deinterleave mode (dimode), and outputs deinterleaved data (data2) and a Reed-Solomon packet sync signal (psync2) that is synchronized with the deinterleaved data, to the Reed-Solomon decoding unit 110.
Then, the Reed-Solomon decoding unit 110 subjects the data (data2) to Reed-Solomon decoding, and outputs decoded data (data3) to the output terminal 113, as well as outputs a Reed-Solomon packet sync signal (psync3) that is synchronized with the data (data3) to the output terminal 111, and further outputs a Reed-Solomon packet error signal (perror) that is synchronized with the data (data3) to the output terminal 112.
As described above, in the prior art error correction apparatus, the deinterleave mode majority judgement unit 109 extracts a predetermined number of deinterleave modes which are inserted into inputted data (data1) regularly (for example, for each frame), and makes majority decision to decide a deinterleave mode, thereby realizing the deinterleaving.
According to the prior art error correction apparatus, a demodulation unit that is provided at the previous stage of the deinterleave unit requires time for clock reproduction from a carrier, or lead-in time for detecting frame synchronization/segment synchronization. Because the frequency of the carrier is high, the time to reproduce the clock is relatively short. In addition, the frame synchronization/segment synchronization is usually detected on the basis of the majority decision, and thus almost the same lead-in time as that for detecting a deinterleave mode is required. As described above, the lead-in time for the deinterleave judgement occupies a large proportion of the entire lead-in time for the demodulation system, and therefore it is thought that the entire lead-in time of the demodulation system is greatly affected.
However, since a transmission efficiency should be enhanced, in order to transmit a large quantity of data, the proportion occupied by deinterleave modes in all the data becomes small, and the demodulation system entirely requires a long lead-in time.